BRISBANE, Calif., Feb. 25, 2014 (GLOBE NEWSWIRE) -- Hyperion Therapeutics, Inc. (Nasdaq:HPTX) today announced that results of the Phase 2 trial of glycerol phenylbutyrate (GPB) for the treatment of hepatic encephalopathy (HE) were published in the March 2014 issue of Hepatology. The study met its primary endpoint with significantly fewer patients treated with GPB experiencing HE events as compared to patients receiving placebo. The randomized, double-blind, placebo-controlled Phase 2 trial enrolled 178 patients with cirrhosis, including 59 already taking rifaximin, who had experienced two or more HE events in the prior six months. Patients were randomized in a 1:1 ratio to receive 6 mL GPB or placebo, orally, twice daily for 16 weeks. The primary endpoint was the proportion of patients with HE events. GPB significantly reduced the proportion of patients who experienced a HE event (21% compared to 36%, p=0.02), as well as the time to first HE event (hazard ratio = 0.56, p < 0.05) and total HE events (35 versus 57, p=0.04) and was associated with fewer HE hospitalizations (13 versus 25, p=0.06). Among the subgroup of patients not taking rifaximin at baseline, there was a highly statistically significant reduction among patients randomized to GPB both in the percentage of patients with events (10% versus 32%; p<0.01) and the total number of HE events (7 versus 31; p < 0.001). Among patients taking rifaximin at baseline, there was no difference in the proportion of patients with events or total events, although a non-significant trend was observed with respect to fewer hospitalizations in patients randomized to GPB. A similar proportion of patients in the GPB (79%) and placebo group (76%) experienced adverse events. "We and our investigators are gratified by the results and new information the trial has yielded regarding the importance of ammonia in the pathogenesis of HE. We look forward to initiating enrollment in our pivotal Phase 3 trial late this year or early 2015 with the ultimate goal of providing HE patients with a new therapeutic alternative," said Bruce Scharschmidt, M.D., chief medical officer at Hyperion.